Cathode-ray oscillator tube



1953 G. c. SZIKLAI 2,638,561

CATHODE-RAY OSCILLATOR TUBE Filed Oct. so, 1946 Zhwentor George G JZz'k/az' WM 4 (Ittomeg Patented May 12, 1953 CATHODE-RAY OSCILLATOR TUBE George C. Sziklai, Princeton, N. J., assignor to Radio Corporation of America, a corporation of Delaware 7 Claims.

This invention relates to the production of high frequency oscillations and more particularly to the control and variation of the frequency thereof.

Cathode ray tubes have heretofore been made to produce oscillations by so introducing the electrons of the beam into a magnetic field that they are caused to spiral around the magnetic lines and land alternately on targets connected to the terminals of a resonant circuit. This type of oscillator is disclosed in the patent granted to Irving Wolff, January 10, 1941, No. 2,244,753. It is an object of this invention to provide means for controlling the frequency of the oscillations of this type of oscillators by an outside agency such as FM signal variations.

Another object of the invention is to provide means in a beam type oscillator tube for frequency modulating the output thereof.

Another object of the invention is to provide a beam type amplifier of high power for frequency modulated waves of low power.

Other objects of the invention will appear in the following description reference being had to the drawings in which:

Fig. l is a view of a section of a cathode ray tube diagrammatically illustratin the invention;

Fig. 2 is a View of a modification;

Fig. 3 is a view of the target of the tube of Fig. 1; and

Fig. 4 is a view of a modified form of target.

Referring to Fig. 1, the tube embodying the invention may take various forms but by way of example I have shown an evacuated glass envelope l around which is a coil 2 for producing a direct current magnetic field, preferably parallel to the axis of the tube. Iron or steel discs 2 may be used to substantially eliminate the fringe field. A gun G comprising a cathode 3, grid l and first anode 5 produces a beam of electrons 6 in a given direction at an angle to the tube axis into the magnetic field produced by coil 2. At the end of the tube Opposite the gun G in a, plane normal to the tube axis are positioned two spaced second anodes or targets l and 8 of suitable form, fiat semi-circular plates being shown (Fig. 3). These targets are connected to a tuned circuit comprising the secondary coil 9 and condenser ill. The potential center of the tuned circuit is connected to the positive terminal of a voltage source, to the negative terminal of which is connected the cathode 3. The grid 4 may be connected to a slightly more negative terminal than the cathode as is usual in the art.

The first anode 5 should be connected to a positive terminal of this source of less potential than that connected to the tuned circuit. Two spaced screens l! and 12 are placed so as to be in the path of the beam. They may be positioned perpendicular to the axis of the tube or alternately to the axis of the gun. A signal source typified by a transformer I3 may have its secondary coil it connected between the two screens.

The operation of the invention may be described as follows:

The beam enters the axial magnetic field in a given direction at an angle thereto and this gives the electrons a radial component of velocity which causes them to spiral around the magnetic lines of force and land, say on target 8. The landing velocity or the target material may be such that the ratio between secondary and primary electrons is less than unity so the target 8 goes negative and this causes the target i to swing positive. The electrons of the beam are then repelled and spiral around and land on target I, whereupon the action is repeated. By correlating the period of resonance of the circuit 9, it connected to the targets with the period of revolution of the electrons in a complete spiral, oscillations will be sustained and oscillating current will be produced in the circuit 9, Ill.

The signal input to screens H and 12 which may be a frequency modulated wave produces a varying high frequency field in a portion oi the path of the beam electron. This velocity modulates the beam and the spiral paths of the electrons are in effect compressed and expanded in synchronism with the FM signal variations of the input of the tube. These vary the landing of the electrons on the targets so that the frequency of oscillation in the output is varied. The tuning may be made broad enough to permit the signal field variation to trigger the oscillations somewhat similar to the locking-in of oscillations in feedback oscillators. Thus, the FM signal input of low power is amplified at the output 9, H).

In the modification of Fig. 2, the gun introduces the beam 6 into the magnetic focusing field parallel to the magnetic lines and the radial velocity component is produced by the electrostatic deflecting plates l5, it which are connected to positive and negative terminals of a direct current source of sufficient potential difference to deflect the beam into the magnetic field at the desired angle. A bucking coil 2" may be used to reduce the fringe field of the coil 2 3 Due to the curvature of the plates I5, I6 the electrons of the beam are velocity sorted as in my application filed August 25, 1945, Serial No. 612,651, which is now U. S. Patent #2534537 granted December 19, 1950. In this figure the two grids II, I2 are connected to rings I'I, I8 sealed in the envelope I and contacting the capacity edges of a cavity resonator I9 of tire casing form. The screens converge downward in Fig. 2 so that the field varies inversely with the velocity of the electrons. That is, the

strongest field oscillates the slow electrons, and

the weakest field oscillates the fastest electrons. The signal may be introduced by coil 20. The

targets may also be a slitted hollow'box which forms a cavity resonator 2| from which the signal is taken at 22. The half sides 23, 24 formed the capacity members of said cavity resonator and by the slot 25 constitute the targets similar to I and 8 of Fig. 1.

The operation of the tube in Fig. 2 is as follows:

The beam containing electrons of a range of velocities according to the Maxwellian law is sub,

jected to the electric field of plates I5, I6 which deflects them along curved paths. The fast electrons are deflected least and the slow ones are deflected most. This causes the electrons of different velocities to enter the field between the screens II and I2 of the cavity resonator I9 in such position that they are equally acted upon by the field. This is because the converging screens vary the field inversely with the velocity of the electrons therein. The electrons after leaving the screen I2 of the cavity resonator drift in the accelerating field and the slow electrons fall behind and bunch up with the succeeding fast electrons so that they arrive together at the cavity resonator 2|, which is correctly positioned for this purpose. The oscillation frequency of the beam is controlled by the input signal of in the same way as in Fig. 1. That is, weak FM input signals are amplified to strong signals at output coil 22.

The advantage of the tube of Fig. 2 over that of Fig. 1 is that substantially all electrons arrive at the output resonator in phase and maximum effects are produced.

The high frequency energy of the beam is introduced into the cavity resonator by the electromagnetic field of the electrons as they spiral across theslot in their travel from plate 24 to plate 23and vice versa. The field produces high frequency alternating potentialities on the inside surfaces adjacent the slot and the current flow produced thereby sets up an electromagnetic field passing through output coil 22.

Instead of introducing a frequency modulated carrier wave into the tube for amplification one may introduce AM signals in the input circuit and these then will frequenc modulate the oscillations of the beam at the output.

By constructing the target in four sections,-

as shown in Fig. 4 the frequency will be doubled by proper choice of parameters of the tube. The

frequency may be multiplied as much as desiredby multiplying the sectors of the target, alternate sectors being connected together with each series" of sectors connected to a side of the tuned circuit 9, I0.

Various other modifications may be used without departing from the spirit of the invention.

What I claim as new is: 1. A cathode ray beam amplifier tube comprising a tuned circuit having target plates, means for producing a uniform magnetic field in the.

converging toward the paths of the slowest electrons, to subject the electrons to electric signal fields inversely varying with their velocity, said target plates being located where the electrons of various velocities are bunched together by fast electrons overtaking slow electrons.

2. A cathode ray tube having means for producing a magnetic field axially thereof, means includin an electron gun for projecting an electron beam into said magnetic'field in a given direction at an angle to the tube axis with one velocity component in the direction of the lines of said field and another velocity component perpendicular thereto, a pair of spaced anodes mounted in said field in a plane normal to the tube axis, a pair of screens between said electron gun means and said anodes and spaced apart along the lines of said magnetic field, output terminals coupled to said anodes and input terminals coupled to said screens.

3. A cathode ray tube having means for producing a magnetic field axially thereof, a cathode ray gun mounted in said tube at an angle to the longitudinal axis thereof to project electrons into said field in a given direction with velocity components in the direction of and perpendicular to the lines thereof, a pair of spaced anodes mounted in said field in a plane normal to the tube axis, a pair of screens between said cathoderay gun and said anodes and spaced apart along the lines of said field, output terminals connected to said anodes and input terminals connected to said screens.

4. A cathode ray tube comprising a coil for producing a magnetic field axially thereof, a cathode ray gun mounted in said tube at an angleto the longitudinal axis thereof to project electrons into said field in a given direction with one velocity component in the direction of the linesthereof, and another velocity component perpendicular thereto, a pair of spaced anodes mounted at one end of said coil in a plane normal to the tube axis, a pair of screens between said gun and the other end of said coil, input terminals connected to said screen and output terminals connected to said anodes.

5. A cathode ray tube comprising means for producing a magnetic field axially thereof, a pair of curved electrodes spaced apart and inclined to the lines of said field, a cathode ray gun adapted to project a beam of electrons between said electrodes and into said field in a given direction ,at an angle thereto with one velocity component in the direction of the lines of said field and another component perpendicular thereto, a pair of output anodes in said field in a plane normal to the tube axis, a cavity resonator between the output anodes and said electrodes, screens connected to-the capacity members of said cavity resonator converging towards each other at one side thereof, an input coil in said cavity resonator and an output coil coupled to said anodes.

6. An oscillator including means for producing a magnetic field, means including an electron gun for projecting a beam of electrons into said magnetic field in a given direction at an angle thereto with one velocity component in the direction of the lines thereof and another velocity component perpendicular thereto, a pair of spaced anodes mounted in said field in a plane normal to said field, a tuned output circuit coupled between said anodes, whereby during operation of said oscillator the beam is caused to spiral around the lines of said magnetic field and lands on one of said anodes until repelled thereby and caused to land on the other anode, thus generating oscillations in said tuned circuit, and means for varying the velocity of the electrons of said beam prior to entrance into said magnetic field, to vary the frequency of said oscillations.

7. An oscillator according to claim 6, wherein said last named means comprises a pair of electron-permeable screens spaced along the beam path between said electron gun and said anodes, and means for applying a modulating voltage between said screens.

GEORGE C. SZIKLAI.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,096,460 Llewellyn Oct. 19, 1937 2,214,729 Hickok Sept. 27, 1940 2,232,050 Clavier et a1. Feb. 18, 1941 2,272,165 Varian et a1 Feb. 3, 1942 2,390,250 Hansell Dec. 4, 1945 2,409,222 Morton Oct. 15, 1946 2,413,276 Wolff Dec. 24, 1946 FOREIGN PATENTS Number Country Date 508,354 Great Britain Nov. 4, 1938 

